The present invention relates generally to medical devices and, in preferred embodiments thereof, more particularly provides improved catheter apparatus, and associated methods, for flowing an anesthetic or other fluid into the epidural space of a patient.
Anesthetizing the spinal nerves is conventionally effected by inserting a small diameter hollow needle member into the epidural space (through, for example, a selected interspinous ligament) and then passing the distal end of a smaller diameter catheter member inwardly through the inserted needle into the epidural space. The typical epidural needle is configured at its tip in a manner such that the distal catheter end exits the needle tip in a direction generally transverse to the length of the needle.
To facilitate retention of the distal catheter end within the epidural space after the needle is withdrawn, it is common practice to insert the distal catheter end portion a considerable distance into the epidural space. After catheter insertion therethrough, the needle is withdrawn and an anesthetic fluid is flowed through a lumen within the catheter and outwardly through the distal catheter end within the epidural space. An example of this conventional procedure, using a dual lumen epidural catheter, is illustrated and described in U.S. Pat. No. 4,737,146 to Amaki et al.
While this general procedure is widely used and accepted, it is not entirely free from problems, limitations and disadvantages. For example, the need to insert the distal catheter end a considerable distance into the epidural space raises the possibility of the inserted catheter portion undesirably "migrating" into an adjacent blood vessel, the subarachnoid space, or out a nerve root sleeve, instead of remaining wholly in the epidural space as intended. Additionally, it is often somewhat difficult to precisely control the actual placement of the fluid lumen outlet within the epidural space since the inserted distal catheter end portion (which, of course, is not visible to the person inserting it) can be deflected within the epidural space and come to rest at an unintended location therein, such as a nerve root sleeve.
Further, despite the offsetting of the distal catheter end from its insertion point, the catheter may be quite easily dislodged and pulled out of the epidural space by, for example, patient movement, or the catheter being bumped by another object. Also, in those instances when two epidural catheters are present simultaneously at different spinal levels within a patient's epidural space, the advancement of the catheters to prevent their slipping out can result in their tangling, thereby creating problems in their removal. In an attempt to alleviate this dislodgement problem it is common practice to tape the catheter to the skin at its entry point, or to "tunnel" an adjacent portion of the catheter under the patient's skin. Neither solution to this catheter dislodgement problem has proven to be entirely satisfactory, as neither involves direct fixation of the distal catheter tip.
Another catheter-related problem presented in applications utilizing an insertion needle is that the typical dual lumen catheter element is provided at its proximal or fluid inlet end with a fixed inlet structure (for example, of a "Y" configuration) which is considerably larger, in a lateral cross-sectional sense, than the balance of the elongated catheter element. This conventional proximal catheter end configuration, in an epidural catheter, is illustrated in the aforementioned U.S. Pat. No. 4,737,146 to Amaki et al. Examples of this laterally enlarged "Y" configuration at the proximal end of a non-epidural catheter are representatively illustrated in U.S. Pat. No. 3,482,576 to Ericson et al; U.S. Pat. No. 3,818,903 to Bleecker; U.S. Pat. No. 4,154,244 to Becker et al; U.S. Pat. No. 4,207,899 to Patel; and U.S. Pat. No. 4,259,960 to Taylor.
The laterally enlarged inlet configuration on the proximal end of conventional dual lumen catheter elements captively retains the epidural insertion needle on the catheter element after the distal end of the catheter has been inserted into the epidural space and the needle has been subsequently withdrawn from the patient's body. This adds undesirable bulk to the overall catheter structure, which must often be left in place for considerable periods of time. Additionally, the withdrawn needle has a tendency to slide back and forth along the outwardly projecting catheter element portion and must usually be taped or otherwise secured to the catheter to prevent this awkward and undesirable shifting of the withdrawn needle along the length of the catheter element, and possible cutting of the catheter by the sharp end of the needle. In addition, the exposed needle point is a hazard both to the patient and to the attending medical personnel.
Like conventional catheters used in other applications, conventional epidural catheter elements also have a tendency to undesirably shut off fluid flow therethrough when sharply bent or kinked due to the heretofore unavoidable pinching shut of their internal fluid flow lumens. Accordingly, considerable care must be taken to assure that the installed catheter is kept free from sharp bends and kinks. This is often a somewhat difficult task, particularly when a long catheter is used and left in place for extended periods of time without professional supervision. Shifting of the patient's body can easily pinch off the catheter lumen or lumens. The catheter may also be kinked by the combination of outward migration of the non-fixed distal catheter tip portion and the fixation of the catheter at the skin or other non-distal location creating redundant catheter length.
In view of the foregoing it can readily be seen that a need exists for various improvements in epidural catheter apparatus and associated methods of flowing anesthetic or other fluids into the epidural space. It is accordingly an object of the present invention to provide such improvements.